As a veteran of the American school system, I consider myself to be an expert on teachers. Many teachers are unique and different in their own way but when it comes down to these three things they are all the same: discipline, grading system, and attendance. No matter how young or old they are all these methods are alike.
No teacher gets aggravated more than when the students misbehave. When such student or students start to act up the teacher always, goes ahead with the no-tolerance attitude. Then, the teacher punishes the student enough so there will be no more 'activity' in the classroom.
The next aspect is the grading system. Every teacher I have ever known has always been loose on this system. There have been several times when I or someone else has gotten a 92% in the class, and the teacher has graciously rounded up.
Also, the grading system counts on effort, too. If a teacher sees you trying hard but not succeeding she will boost your grade to what that someone put in to it.
Lastly, attendance is the last thing that teacher have in common. This is the thing that they are bothered by the most. Even if a student was to come in the classroom with a pass from a teacher, you will still see irritation in his/her eyes. Basically, because the reason they get like this is, they want to get the lesson on with but is disturbed with this distraction.
Teachers don't realize how alike they are, even though they try to be different. I should know, I been going to school for 14 years and had over 35 teachers.